B-type natriuretic peptide (BNP) is a 32-amino-acid polypeptide secreted by the ventricles of the heart in response to excessive stretching of myocytes (heart muscles cells) in the ventricles. The levels of BNP are typically elevated in patients with left ventricular dysfunction. Further, BNP levels correlate with both the severity of symptoms and the prognosis in congestive heart failure. Additionally, BNP appears to be a useful marker of cardiovascular risk, even in people with no clinical evidence of cardiovascular disease.
Levels of BNP are typically measured based on blood samples. For example, 5 mL of blood can be collected into a tube containing potassium EDTA, and the level of BNP can be measured using a Triage™ BNP Test available from Biosite Inc. of San Diego, Calif. However, because most techniques for measuring levels of BNP require blood samples, they are not practical for chronic monitoring of levels of BNP. Nevertheless, it would be advantageous if systems and methods were available for providing chronic monitoring of levels of BNP.
Heart failure (HF) is a condition in which a patient's heart works less efficiently than it should, resulting in the heart failing to supply the body sufficiently with the oxygen rich blood it requires, either at exercise or at rest. Congestive heart failure (CHF) is heart failure accompanied by a build-up of fluid pressure in the pulmonary blood vessels that perfuse the lungs.
Chronic diseases such as CHF require close medical management to reduce morbidity and mortality. Because the disease status evolves with time, frequent physician follow-up examinations are typically necessary. At follow-up, the physician may make adjustments to the drug regimen in order to optimize therapy. This conventional approach of periodic follow-up is unsatisfactory for some diseases, such as CHF, in which acute, life-threatening exacerbations can develop between physician follow-up examinations. Accordingly, it would be advantageous if systems and methods were available for providing chronic monitoring of a patient's HF condition.
Myocardial infraction (MI) (also known as a heart attack) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen, causing injury to the heart muscle. Injury to the heart muscle causes chest pain and chest pressure sensation. If blood flow is not restored to the heart muscle within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for six to eight hours at which time the heart attack usually is “complete.” The dead heart muscle is eventually replaced by scar tissue. When an MI occurs, it is important that treatment be provide to the patient as soon as possible, so that sustained damage to the patient's heart can be prevented. However, some MIs are silent, meaning they are non-symptomatic, and thus a patient may be unaware that an MI occurred. Further, even if a MI is symptomatic, a patient may not be in a condition that they can notify a physician of the MI.
A goal of the management in of MI is to salvage as much myocardium as possible during the acute phase of MI to prevent further complications. This is because as time passes, the risk of damage to the heart muscle increases. Accordingly, it would be useful if systems and methods were available for chronically monitoring for acute MIs, and risks thereof.